Question: The grades on a history midterm at Gardner Bullis are normally distributed with $\mu = 73$ and $\sigma = 4.0$. Christopher earned a n $85$ on the exam. Find the z-score for Christopher's exam grade. Round to two decimal places.
Explanation: A z-score is defined as the number of standard deviations a specific point is away from the mean We can calculate the z-score for Christopher's exam grade by subtracting the mean $(\mu)$ from his grade and then dividing by the standard deviation $(\sigma)$ $ { z = \dfrac{x - {\mu}}{{\sigma}}} $ $ { z = \dfrac{85 - {73}}{{4.0}}} $ ${ z \approx 3.00}$ The z-score is $3.00$. In other words, Christopher's score was $3.00$ standard deviations above the mean.